JP3828271B2 - Cap for electronic parts and semiconductor laser using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cap for an electronic component comprising a metal shell having a window at the top and an opening that can be joined to a stem at the bottom, such as a can seal type semiconductor laser. In more detail, the glass of the window portion of the cap is not damaged even when a strong external pressure is applied from the upper surface of the cap of the electronic component in which the cap is assembled by pressing the cap into the stem. The present invention relates to an electronic component cap and a semiconductor laser using the same.
[0002]
[Prior art]
The can-seal type semiconductor laser has a structure such that an explanatory diagram of a partial cross section is shown in FIG. In FIG. 7A, a laser chip 23 is mounted on a heat sink 21 a integrated with a stem 21 via a silicon submount 22. A lead 26 is insulated from the stem 21 and hermetically sealed (hermetic sealing), and a lead 28 is connected to the stem 21 by welding or the like. One electrode terminal of the laser chip 23 is wire-bonded to the lead 26 via the silicon submount 22. The other electrode of the laser chip 23 is connected to the lead 28 through the heat sink 21a. A cap 24 is hermetically sealed around the cap 21 by welding or the like.
[0003]
A window portion by a through hole is provided on the top portion of the cap 24 to take out light from the laser chip 23, and a window glass 25 is bonded with a low melting point glass (not shown) or the like to make the inside airtight. The cap 24 is welded to the stem 21 in a state where the window glass 25 is bonded to the cap 24 in advance. In many cases, this welding is performed by electric resistance welding. In this case, in order to concentrate the current and secure the welding, as shown in FIG. 7B, a projection-like projection 24a is formed on the bottom surface of the cap 24. Is formed. Not only a semiconductor laser but also a cap having a window portion for hermetic sealing, a structure used for a phototransistor, a photodiode, a light emitting diode (LED) of a metal cap, etc. has a structure as shown in FIG. It has become.
[0004]
On the other hand, in the above structure, when attaching a cap, it is necessary to obtain a hermetic seal by welding with a stem. However, the welding conditions vary widely, a stable hermetic seal cannot be obtained, and since it has a projection, miniaturization is difficult. Therefore, as disclosed in JP-A-9-283852, an attempt has been made to obtain a hermetic seal by press-fitting a cap into a stem.
[0005]
[Problems to be solved by the invention]
As described above, when the cap with the window glass sealed is to be press-fitted, the window glass or the low-melting glass of the adhesive is likely to crack or crack. Therefore, in Japanese Patent Laid-Open No. 9-283852, in order to solve the problem, the protrusion is formed in a ring shape on the outer peripheral surface of the top, but when mass production is performed by an automatic machine, FIG. As shown in (b), when the dimensional difference between the inner diameter A of the cap 24 and the outer diameter B of the fitting portion of the stem 21 (B is larger than A) is not controlled to about 10 to 20 μm, Since an external force is applied to the bonding portion and the window glass 25 may be peeled off, there is a problem that the management of the variation in the inner diameter and the outer diameter of the cap and the stem is difficult and the mass productivity is lacking. In FIG. 6, 29 is an adhesive such as low-melting glass.
[0006]
The present invention has been made to solve such a problem. When a cap having a light transmitting member such as a window glass is hermetically sealed to a stem by press fitting, the dimensional relationship is not severe. However, an object of the present invention is to provide a cap for an electronic component having a structure that does not crack or break the glass or adhesive of the window.
[0007]
Another object of the present invention is to provide a semiconductor laser having a structure in which parts management is easy and a simple assembling method in which a cap is press-fitted into a stem is employed and a window portion is not damaged.
[0008]
[Means for Solving the Problems]
The cap for an electronic component according to the present invention is an electronic device in which a light transmitting member is bonded to the window of a cylindrical metal shell having a window formed at the top and an opening that can be joined to the stem by press fitting. The cylindrical cap of the metal shell has a stepped portion so that the thickness on the opening side is thinner than the thickness on the top side over a range longer than the length of the portion press-fitted into the stem. Is formed.
[0009]
With this structure, when the cap is press-fitted into the stem, the force that spreads on the opening at the bottom of the cap is absorbed by the thin part of the cylindrical part, and the thick part on the upper side is absorbed by the thick part. Hard to apply force. For this reason, the force applied to the window glass bonded to the window portion or the low-melting glass of the adhesive is very weak, and cracks and cracks are hardly generated.
[0010]
By forming the protrusion on the outer peripheral surface of the top of the metal shell in a ring shape, the light transmitting member such as a window glass and the bonded portion thereof are strengthened against the pressing force from the top, and the window portion is further layered. Peeling is reduced and reliability is improved.
[0011]
The semiconductor laser of the present invention has a stem, a laser chip mounted on a heat sink provided in the stem, a window portion at the top and a cylindrical portion that can be fitted to the stem at the bottom, A cap that hermetically covers the periphery of the cap, and the light transmitting member is fixed to the window portion, and the length of the stem-side wall is longer than the length of the portion where the cylindrical portion is fitted to the stem. The thickness is thin and the top side is formed thick, and is fitted into the stem by press-fitting.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Next, the electronic component cap of the present invention will be described with reference to the drawings.
[0013]
As shown in the cross-sectional explanatory view of one embodiment of the cap 10 for an electronic component of the present invention, a window portion 13 is formed on the top portion of the cylindrical portion 11 of the metal shell, and a stem can be joined to the bottom portion. An opening 14 is formed. A light transmitting member 15 such as glass or plastic is bonded to the window portion 13 with an adhesive 16 such as low melting point glass so that the airtightness can be maintained. The cylindrical portion 11 of the metal shell is characterized in that a step portion 11a is formed so that the thickness t on the opening 14 side is thinner than the thickness T on the top side.
[0014]
The metal shell having the window portion 13 at the top of the cylindrical portion 11 is formed, for example, by drawing a Kovar plate or the like. During the drawing process, a through hole serving as a window 13 is provided at the top, and an opening 14 for joining the stem is provided at the bottom. The aforementioned stepped portion 11a is formed by providing a step in a convex mold for drawing, and can be thin on the opening 13 side and thick on the top side. The difference between the thin portion and the thick portion may be such that the force at the time of press-fitting can be absorbed by the thin portion, and a difference that is not transmitted as much as possible to the thick top portion is provided. If the material is made as thin as possible using a Kovar plate, the thin part is about 0.13 to 0.17 mm, and the thick part is about 0.05 mm thicker. The window portion 13 is for passing laser light of a laser chip sealed inside, for example, or for passing light to be received. The window portion 13 needs to transmit light, while the inside is hermetically sealed. In order to protect an element such as a laser chip, a light transmitting member 15 such as a window glass is adhered by an adhesive 16 such as a low melting point glass.
[0015]
As a specific example of the cap used for the semiconductor laser, for example, in the structure shown in FIG. 1, the height L of the cap 10 is about 3 mm, the outer diameter D is about 2.5 mm, and the thickness t of the thin portion is 0.15 mm. The thick part is formed with a thickness T of about 0.2 mm (inner diameter A is about 2.2 mm). And the position M from the lower end part which provides the level | step-difference part 11a is provided in the range of about 1.4-2.2 mm. That is, the height of the fitting portion with the stem is about 1.4 mm from the lower end, and preferably higher than that, and the position of the lower surface of the window glass is about 2.15 mm from the lower end (the window glass The thickness is about 0.2 mm) and falls within that range.
[0016]
In the example shown in FIG. 1, a ring-shaped protrusion 12 is formed at the outer peripheral end of the upper surface of the top of the cap 10. This protrusion 12 is also provided to prevent cracks in the window glass. That is, when a pressure is applied to the entire top surface of the cap to press fit into the stem, a tensile force is applied to the low melting point glass portion used as the window glass or adhesive, and cracks and cracks are likely to occur. By being provided, the tensile force toward the window glass 15 part does not work, and the force is easily transmitted to the lower end side through the cylindrical part 11. The protrusion 12 is formed with a height H of about 0.03 mm and a width W of about 0.25 mm.
[0017]
Next, the window 10 is used as the light transmitting member 15 and the cap 10 is bonded with low melting point glass as the adhesive 16, and the position from the lower end of the stepped portion 11a is constant at 1.4 mm, and the inner diameter of the cap 10 is fixed. The difference (BA) between A and the outer diameter B of the stem was changed variously, and after the cap was pressed into the stem at about 15 to 20 kg, the load when the window glass dropped by 20 samples was examined. . The results are shown in FIG. 2 comparing the cap S of the present invention with a conventional cap R having no stepped portion. As shown in FIG. 4, the conditions for press-fitting the cap 10 are as follows: the stem 5 is placed on the stem fixing base 17, and the center of the cap 10 and the stem 5 is held by the cap guide 18. A load was applied in the direction of an arrow P by a flat plate-shaped pressurizer 19 that hit the entire outer periphery, and press-fitted. And it measured by measuring the load when a window glass falls off with a tension gauge after thick insertion. Note that FIG. 2 also shows a case where a load is applied to the cap alone without being press-fitted into the stem in order to clarify the distinction from the load at which the window glass based on the cap alone, which is not caused by fitting, falls off.
[0018]
Furthermore, BA is constant at 20 μm, the position M of the stepped portion is variously changed in the range of 1.4 to 2.2 mm, and the lower end of the cap is set to 1.2 mm on the outer periphery of the stem with a constant load of 17 kgf. The maximum principal stress (kgf / mm ² ) applied to the low-melting-point glass of the adhesive when fitted to a depth of 1 mm was examined by simulation. The result is shown in FIG.
[0019]
As is clear from FIG. 2, according to the conventional cap R having no stepped portion, the window glass suddenly falls off when B-A, that is, the overlapping dimension of the inner diameter of the cap and the outer diameter of the stem exceeds 20 μm. While the load (not damaged) is reduced, according to the cap S of the present invention, the load at which the window glass drops off hardly changes even when the thickness is about 40 μm. That is, even if there is a variation in fitting between the cap 10 and the stem, the window glass is not damaged and falls off. In the above-described cap and stem manufacturing process, there is almost no variation in which the fitting dimension exceeds 40 μm. In practice, there is a problem if the strength of the window glass drop-off is constant within the range of 40 μm or less. There is no. Further, as is apparent from FIG. 3, the maximum principal stress is half that of the step portion of 1.4 mm or more compared to the conventional case where the step portion is not provided (the step portion position M is 0). From this result, it can be seen that the stress on the low-melting glass is reduced by forming the stepped portion. In addition, about the position M of the step part, it is necessary to increase the load at the time of press-fitting even if the same fitting is smaller, and it cannot be said that it is generally better that the position M of the step part is small.
[0020]
Next, the semiconductor laser of the present invention using this cap will be described with reference to FIG. 5 (a) and 5 (b) are cross-sectional views on planes shifted by 90 °.
[0021]
5 (a) to 5 (b), reference numeral 1 denotes a cylindrical ring formed by drawing and punching from an iron-based or copper-based metal material having a thickness of about 0.2 to 0.4 mm. The tip portion has a heat sink 1a bent so as to extend upward, and a submount 6 on which a laser chip 7 is mounted is bonded. At the bottom of the cylindrical ring 1, a collar 1b is provided with a width of about 0.3 mm, and a common lead 1c extends downward from a part of the collar 1b. The heat sink 1a and the common lead 1c are simply formed by punching the lead frame and bending it. Moreover, although the notch part which positions in the rotation direction is provided in the collar part 1b, it is not illustrated. In this ring 1, leads 3 and 4 insulated and held by an insulator 2 such as glass are hermetically sealed, and a stem 5 is formed by the cylindrical ring 1, the insulator 2 and the leads 3 and 4. .
[0022]
The submount 6 to which the laser chip 7 is bonded is conveyed to the heat sink 1a by the suction collet, aligned and mounted. The positioning of the submount 6 is performed using the surface F of the flange 1b of the ring 1 as a reference plane. By doing so, when the semiconductor laser is attached to a set such as a CD player, the surface F of the flange 1b is used as a reference, so that accurate positioning can be performed.
[0023]
The submount 6 is formed of, for example, a silicon substrate, and is provided to facilitate the assembly of a small laser chip 7 of about 200 μm × 150 μm. In this example, a light receiving photodiode (not shown) for monitoring the light emission amount of the laser chip 7 is formed on a submount 6 made of a silicon substrate. The electrodes of the laser chip 7 and a photodiode (not shown) are connected to the leads 3 and 4 by wire bonding with gold wires 8, respectively. The other electrodes of the laser chip 7 and the photodiode are connected to the common lead 1 c through the back surface of the submount 6, and the three leads 1 c, 3, 4 extend to the back surface side of the stem 5.
[0024]
A semiconductor laser is manufactured by press-fitting the cap 10 shown in FIG. 1 into the outer peripheral wall of the cylindrical ring 1 of the stem 5 on which the laser chip 7 is mounted. That is, for example, the outer diameter of the cylindrical ring 1 is about 2.23 mm, and the inner diameter of the lower end of the cap 10 is about 2.20 mm, and press-fitting is performed by the same method and conditions as shown in FIG. It is manufactured by.
[0025]
In the above-described example, the protrusion is provided on the outer periphery of the top of the cap. However, by providing the protrusion, it is possible to avoid the concentration of the load on the window with respect to the load from the upper surface of the cap. Therefore, although the step portion is provided even if there is no protrusion, it is possible to suppress the influence of variation in fitting of the fitting portion between the cap and the stem.
[0026]
【The invention's effect】
According to the present invention, conventionally, the difference between the outer diameter of the stem and the inner diameter of the cap has to be suppressed to about 10 to 20 μm. There is no influence of the stress, and a large variation in fitting between the cap and the stem can be allowed. Therefore, it is not necessary to strictly control the dimensions of the stem and cap, and manufacturing management is facilitated, productivity is improved, and it can be applied to mass production. As a result, an inexpensive and highly reliable electronic component such as a semiconductor laser can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional explanatory view of an embodiment of an electronic component cap of the present invention.
FIG. 2 is a diagram showing the relationship of the load at which a window glass drops off with respect to the degree of fitting with a stem when the cap of FIG. 1 is used.
FIG. 3 is a diagram showing the relationship of the maximum principal stress to the low melting point glass with respect to the position of the stepped portion of the cap.
FIG. 4 is an explanatory diagram of a state in which a cap is press-fitted into a stem.
5 is a cross-sectional explanatory view of a semiconductor laser using the cap of FIG. 1. FIG.
FIG. 6 is an explanatory diagram of a relationship between an inner diameter of a cap having a structure in which a cap is press-fitted into a stem and an outer diameter of the stem.
FIG. 7 is an explanatory diagram of a conventional semiconductor laser.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Cap 11 Cylindrical part 11a Step part 13 Window part 14 Opening part 15 Light transmissive member

Claims (3)

A cap for an electronic component in which a light transmitting member is bonded to the window portion of a cylindrical metal shell in which a window portion is formed at the top and an opening that can be joined to the stem by press fitting is formed on the bottom portion. The cylindrical part of the shell has a stepped portion formed so that the thickness on the opening side is thinner than the thickness on the top side over a range longer than the length of the portion press-fitted into the stem. .   The cap for electronic components according to claim 1, wherein a protrusion is formed in a ring shape on the outer peripheral surface of the top of the metal shell. A stem, a laser chip mounted on a heat sink provided in the stem, a cap having a window at the top and a cylindrical portion that can be fitted to the stem at the bottom, and covering the periphery of the laser chip in an airtight manner The cap has a light transmitting member fixed to the window portion, the cylindrical portion has a thin wall thickness on the stem side over a range longer than the length of the portion fitted with the stem , and the cap A semiconductor laser having a thick top portion and press-fitted into the stem.

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